Yes I already asked Lord British how it worls, but I when I used the portal in Trinsic, it did not take me anywhere, I am still in Trinsic, so do you I used it the right way?

Are you using the red portal from the Orb of the Moons or the blue portal in the circle of stones near town?

The blue portal's destination is set by the current phase of the moons.

The red portal's destination is set by the location you target relative to the Avatar. If you imagine a 5x5 grid with the Avatar in the center tile, each of the other tiles will lead to a specific location. (These are mostly different, although IIRC there are two positions for certain destinations.)